Based on a new estimate of what climate change will do to the US economy, the cost could be hundreds of billions of dollars.

A sweeping study out today looks at the potential economic effects of warming down to the county level — and even under the best scenario, it means more heat-related deaths, higher energy bills, and lowered productivity that will widen the gap between rich and poor.

The calculations found every 1 degree increase in global average temperatures shaves about 1.2 percent off the US gross domestic product, currently estimated at $18 trillion. And just as the effects of climate change are expected to hit the world’s poor the hardest, the lowest-income parts of the United States — particularly the Deep South — are likely to see the worst of it, said co-author James Rising, who studies climate impacts at the University of California, Berkeley’s Energy and Resources Group.

“The people who are going to be shouldering a big part of these costs are the one who are least capable of doing that just because they don’t have the levels of incomes you see in many of the states in the North,” Rising said. And since any positive changes fall mainly to the more prosperous northern states, climate change amounts to “a subsidy being paid to Northern, richer states by poorer Southern states.”

The estimates, published in the research journal Science, crunched data ranging from crop losses to crime rates through computer models based on three scenarios. In one, carbon dioxide and other planet-warming emissions are held down enough to limit global average temperatures to 1.5 degrees C (2.7 degrees Fahrenheit) over pre-industrial conditions by 2100 — the aspirational target of the Paris climate accord. A second restricts emissions somewhat, but not enough to keep climate from warming between 2-3°C. In the third, unrestrained emissions lead to warming up to 5°C.

Under a business-as-usual scenario, economic losses could be anywhere from 6.4 to 15.7 percent of GDP — the equivalent of a steep recession, with no rebound. Some counties, particularly in rural Florida, could see losses approaching 30 percent of their economies. The best case foresees as much as 1.7 percent of future growth being shaved off.

Rising said he hopes the data can be used to help communities prepare for what’s coming.
“I think the biggest thing I would hope people recognize out of the work that we’ve done is that we aren’t all going to be receiving the same impacts,” he said.

This is the national average economic damage in the USA. |
Hsiang, Kopp, Jina, Rising, et al (2017)

The projections are based on 29,000 simulations that Rising said took more than 100,000 hours of computer time to run. And while the estimates take into account factors as varied as coastal losses, crop damage, and crime rates, Rising said the biggest driver is increased mortality. Without restraining emissions, heat-related death rates might rival today’s vehicle crashes by the end of the century, Rising said.

This is the projected economic damage from climate change in United States counties. |
Hsiang, Kopp, Jina, Rising, et al (2017)

“By end of century, you’re going to see most of the US have more than a month of dangerously hot and humid days,” Rising said. “Washington [state] is going to be as hot and humid about as Florida currently is by the end of the century under business-as-usual conditions.” Georgia may see two months of summer when going outside will be hazardous to your health, he said — but northern states will benefit from fewer cold-related deaths in the winter.

“On balance, there are going to be 10 or 11 states that on average are going to have fewer deaths because of climate change than without it,” he said. “That ends up being quite a big benefit to those areas.”